John Muir was one of the earliest advocates of the national park idea, and its most eloquent spokesman. Born in Dunbar, Scotland, he moved with his family to a Wisconsin farm in 1849. Muir's father, an itinerant Presbyterian minister, treated him harshly and insisted that he memorize the Bible. By age 11, he was able to recite three-quarters of the Old Testament by heart, and all of the New Testament.

As a sickly young boy in New York City, Theodore Roosevelt learned taxidermy and started his own collection of stuffed specimens. At age 12, he donated some of them – a dozen mice, a bat, a turtle, four birds' eggs and the skull of a red squirrel – to the American Museum of Natural History. Eleven years later, he presented 622 carefully preserved bird skins to the Smithsonian.

Stephen Mather was the first director of the National Park Service. He used his wealth and political connections to take the national park idea in important new directions Mather's love of the parks was highly personal: he had found that time in nature helped him ward off the bouts of depression to which he was prone. Born in California to a family with deep, patrician roots in New England, Mather graduated from the University of California at Berkeley, worked as a reporter for the New York Sun, and then served as sales manager for the Pacific Coast Borax Company, where he demonstrated his special genius for promotion.

Horace Albright served as the first assistant director of the National Park Service under Stephen Mather. A Berkeley graduate, he had arrived in Washington so poor he wore a borrowed suit and took a room at the local YMCA. Like his boss, Albright had become enthusiastic about national parks because of a personal encounter with John Muir. But he was already planning to return home to California to practice law when Mather arrived in Washington; his new boss persuaded him to stay on.

George Melendez Wright was born into a wealthy San Francisco family. His father was a ship's captain and his mother was from one of El Salvador's most prominent dynasties. He exhibited an early interest in the natural world, hiking from San Francisco to California's northern border in his mid-teens, and earning a degree in forestry and zoology from the University of California, Berkeley. During a field trip to Alaska, he was credited with being the first scientist to locate and describe the nest and eggs of the rare surfbird.